The present invention relates to a method and a system for controlling the automatic transmission of an automotive vehicle.
The manual-shifted transmission is superior in fuel economy to the automatic transmission using a torque converter, but has difficulty in a coordinated operation between the clutch and the accelerator at starting an automotive vehicle. If the operation of the accelerator and the clutch at starting the vehicle is not coordinated properly, a great shock occurs when the clutch is engaged, or if the clutch pressure is not sufficient, the engine speed rises sharply, giving rise to a so-called surging. If one tries to engage the clutch abruptly while the engine speed is not high enough or if a car starts on an uphill, the engine will stall.
To solve those problems, efforts are now underway to develop an automated system of clutch operation and gear change by using the mechanism of a manual-shifted transmission, namely, an automatic MT (automatic manual transmission). With respect to clutch control at starting the vehicle, a technique has been disclosed in JP-A-60-11720, for example.
In control of starting or shifting gears with the automatic MT, changes in acceleration caused by releasing and engaging the clutch at starting the vehicle give the occupants discomfort.
A vehicle with an automatic MT transmission has no creep torque, because the clutch for transmitting the driving force from the engine output shaft is in the released condition when the shift lever is in the drive range in contrast to a conventional AT vehicle and provides a lower starting performance than the AT vehicle at starting.
An object of the present invention is to suppress changes in acceleration both at starting and gear shifting by controlling the clutch for transmitting the driving force from the engine output shaft to thereby improve gear-shifting performance.
Another object of the present invention is to produce a creep torque when starting an automotive vehicle to thereby obtain a better starting performance.
According to an aspect of the present invention, a method for controlling an automotive vehicle having a first clutch, mounted between an engine and a gear drive transmission, for connecting or disconnecting torque transmitted from the engine to driving wheels, and torque transmission units disposed between an input shaft and an output shaft of the gear drive transmission, wherein the torque transmission units are of the dog clutch type, and wherein the first clutch is controlled at starting the vehicle or at gear shifting, comprises the steps of controlling the first clutch transmission torque based on a difference between the engine speed and the revolution speed of the transmission input shaft at starting the vehicle, and controlling the engine torque based on the first clutch transmission torque.
According to another aspect of the present invention, a control system for an automotive vehicle having a first clutch, mounted between an engine and a gear drive transmission, for connecting or disconnecting torque transmitted from the engine to the driving wheels, and torque transmission units disposed between an input shaft and an output shaft of the gear drive transmission, wherein the torque transmission units are of the dog clutch type, and wherein the first clutch is controlled at starting the vehicle or at gear shifting, comprises a clutch control unit for controlling the first clutch transmission torque based on a difference between the engine speed and the revolution speed of the transmission input shaft at starting the vehicle, and an engine torque control unit for controlling the engine torque of the first clutch controlled by the clutch control unit.
According to a further aspect of the present invention, changes in acceleration can be suppressed at starting a vehicle or at gear shifting by controlling the clutch for transmitting the driving force from the output shaft of the engine to thereby improve the gear shifting performance.
According to yet another aspect of the present invention, a control system for an automotive vehicle having a first clutch, mounted between an engine and a gear drive transmission, for connecting or disconnecting torque transmitted from the engine to the driving wheels, and torque transmission units disposed between an input shaft and an output shaft of the gear drive transmission, wherein the torque transmission units are of the dog clutch type, and wherein the first clutch is controlled at starting the vehicle or at gear shifting, comprises a driver""s will-detecting unit for detecting a request for starting and acceleration, a request for deceleration and stoppage, or a request for shifting gears; a creep control completion decision unit for deciding whether creep torque generation has been finished or not; and a creep torque generating unit, wherein when the driver""s will detection unit detects brake releasing, the first clutch enters a slipping-engagement state, making the driving force to be transmitted to cause the vehicle to move and when the creep control completion decision unit decides that creep torque generation has been finished, the creep torque generating unit releases the slipping-engagement of the first clutch.
According to a still further aspect of the present invention, a better starting performance by generation of creep torque can be obtained, and the temperature increase and deterioration of the clutch caused by continuance of slips can be avoided.